Avoid extra variable

Author: swissspidy

.github/workflows/reusable-testing.yml

@@ -422,8 +422,7 @@ jobs:
 
           if [[ $WP_CLI_TEST_COVERAGE == 'true' ]]; then
             # The flag was only added in v3.17.0
-            XDEBUG_FLAG=$(composer behat -- --help 2>/dev/null | grep xdebug)
-            if [[ -n $XDEBUG_FLAG ]]; then
+            if composer behat -- --help 2>/dev/null | grep xdebug; then
               ARGS+=("--xdebug")
             fi
           fi